Which is the Most Economical Section of a Channel in Fluid Mechanics? Discussion about most economical section in rectangular channel, trapezoidal channel, triangular channel is given below. A channel is said to be most economical if

●      It gives maximum discharge for a given cross -sectional area and bed shape,

●      It has minimum wetted perimeter, and

●      It involves lesser excavation for the designed amount of discharge.

The following points are worth noting :

1.    The most economical section of a rectangular channel is one which has hydraulic radius equal to half the depth of flow.

2.    The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to half the depth of flow.

3.    The most economical section of a triangular channel is one which has its sloping sides at an angle of 45 degree with the vertical.

4.    The discharge through a channel of rectangular section is maximum when its breadth is twice the depth.

5.    The discharge through a channel of trapezoidal section is maximum when the sloping side is equal to half the width at the top.

6.    The discharge through a channel of circular section is maximum when the depth of water is equal to 0.95 times the diameter of the circular channel.

7.    The velocity through a channel of circular section is maximum when the depth of water is equal to 0.81 times the diameter of circular channel.